In a new radio (NR) technology, a base station sends a downlink signal by using a plurality of beams. The downlink signal may be a downlink synchronization signal block (SS/PBCH block), a system information block, remaining minimum system information, a system information block 1 NR SIB1, a system information block 0 NR SIB0, a semi-statically configured downlink subframe and/or slot and/or OFDM symbol, a reserved downlink signal, a downlink demodulation reference signal (DMRS), or a downlink channel state information-reference signal (CSI-RS). Specifically, the base station covers a cell by using the plurality of beams. During communication between the base station and a terminal, an appropriate beam direction is required for performing communication. The base station requires the appropriate beam direction for receiving a random access preamble sent by the terminal, sending a random access response to the terminal, and the like. The downlink signal is sent in a time division manner. To be specific, different downlink signals are sent in different time periods, and random access preambles sent by the terminal are also received in different time periods. In addition, in the NR technology, a maximum quantity of downlink signals in one downlink signal set may vary depending on different frequency bands. For example, below 3 gigahertz (GHz), the maximum quantity of downlink signals in one downlink signal set is 4; at 3-6 GHz, the maximum quantity of downlink signals in one downlink signal set is 8; above 6 GHz, the maximum quantity of downlink signals in one downlink signal set is 64. All downlink signals in a downlink signal set are mapped to different slots and orthogonal frequency division multiplexing (OFDM) symbols within a 5-millisecond (ms) window.
Specifically, a downlink signal set is sent periodically, and a quantity of actually sent downlink signals in a downlink signal set may not be a maximum quantity. For example, below 6 GHz, eight bits are used to indicate whether eight downlink signals are actually sent; above 6 GHz, whether downlink signals are actually sent is indicated in an 8+8 manner: 64 downlink signals are divided into eight groups, each group includes eight downlink signals, eight bits are used to indicate whether the downlink signals in each group are sent, and another eight bits are used to indicate whether eight downlink signal sets are sent.
However, a period for sending a downlink signal set in the NR technology is relatively short. A minimum period may be 5 ms. In other words, downlink signals may be sent in nearly all slots in one system frame. Correspondingly, a random access preamble sent by the terminal is configured in an uplink time, and therefore a time in which the base station sends a downlink signal may conflict with a time in which the terminal sends an uplink random access preamble. The foregoing discussion is a discussion regarding ongoing design efforts for the NR and is not an admission of being prior art.